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QuarkoniumDecayer.cc
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QuarkoniumDecayer.cc
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// -*- C++ -*-
//
// This is the implementation of the non-inlined, non-templated member
// functions of the HeavyDecayer class.
//
#include "QuarkoniumDecayer.h"
#include <ThePEG/PDT/EnumParticles.h>
#include <ThePEG/PDT/DecayMode.h>
#include <ThePEG/Interface/ClassDocumentation.h>
#include <ThePEG/Interface/Parameter.h>
#include "Herwig++/Utilities/Kinematics.h"
#include <ThePEG/Repository/EventGenerator.h>
#include <ThePEG/Repository/Repository.h>
#include <ThePEG/Utilities/Rebinder.h>
#include <ThePEG/Interface/Reference.h>
#include <ThePEG/Interface/Parameter.h>
#include <ThePEG/Persistency/PersistentOStream.h>
#include <ThePEG/Persistency/PersistentIStream.h>
#include <ThePEG/Utilities/Math.h>
#include "Herwig++/Utilities/HwDebug.h"
#include <ThePEG/Handlers/HandlerGroup.h>
#include <ThePEG/Handlers/Hint.h>
#include <ThePEG/EventRecord/Event.h>
#include <ThePEG/Handlers/EventHandler.h>
using namespace Herwig;
using namespace ThePEG;
QuarkoniumDecayer::~QuarkoniumDecayer() {}
void QuarkoniumDecayer::Init() {
static ClassDocumentation<QuarkoniumDecayer> documentation
("Class to decay all particles in HERWIG by the algorithms used in HERWIG 6.4");
static Parameter<QuarkoniumDecayer, int>
interfaceME("MECode", "The code for the ME type to use in the decay",
&Herwig::QuarkoniumDecayer::MECode, 0, 0, 0, true, false, false);
static Reference<QuarkoniumDecayer, GlobalParameters>
interfaceGlobal("GlobalParameters",
"The class that has the info of the effectiveGluonMass",
&Herwig::QuarkoniumDecayer::global, 0, 0, 0, true, false,
false);
}
ClassDescription<QuarkoniumDecayer> QuarkoniumDecayer::initQuarkoniumDecayer;
bool QuarkoniumDecayer::accept(const DecayMode &dm) const {
if(dm.products().size() == 3 || dm.products().size() == 2)
return true;
return false;
}
/******
*****/
ParticleVector QuarkoniumDecayer::decay(const DecayMode &dm, const Particle &p) const
{
if( HERWIG_DEBUG_LEVEL >= HwDebug::full) {
generator()->log() << "Hw64Decay::decay called on " << p.PDGName()
<< "\n";
}
ParticleVector partons = dm.produceProducts();
Lorentz5Momentum products[4]; // Shouldn't be any bigger!
Energy gluMass = 0.750*GeV;
if(!global) {}//cout << "Global is null!\n";
else gluMass = global->effectiveGluonMass();
for(unsigned int i = 0; i<partons.size(); i++) {
if(partons[i]->id() == ParticleID::g)
products[i].setMass(gluMass);
else products[i].setMass(partons[i]->mass());
}
//cout << "generating a quarkonium decay " << dm.tag() << endl;
if(partons.size() == 3) {
// 3-gluon or 2-gluon + photon decay
if(MECode == 130) { // Ore & Powell orthopositronium matrix element
double x1, x2, x3, test;
do {
Kinematics::threeBodyDecay(p.momentum(), products[0], products[1],
products[2]);
x1 = 2.*(p.momentum()*products[0])/sqr(p.mass());
x2 = 2.*(products[1]*products[2])/sqr(p.mass());
x3 = 2. - x1 - x2;
test = sqr(x1*(1.-x1)) + sqr(x2*(1.-x2)) + sqr(x3*(1.-x3));
test /= sqr(x1*x2*x3);
} while(test < 2.*generator()->rnd());
} else Kinematics::threeBodyDecay(p.momentum(), products[0], products[1],
products[2]);
for(unsigned int i = 0; i<partons.size(); i++)
partons[i]->set5Momentum(products[i]);
// Now set colour connections
if(partons[2]->id() == ParticleID::g) {
partons[0]->colourNeighbour(partons[1]);
partons[1]->colourNeighbour(partons[2]);
partons[2]->colourNeighbour(partons[0]);
//cout << "Colour connecting : " << partons[0]->PDGName() << "-->"
// << partons[1]->PDGName() << "-->" << partons[2]->PDGName()
// << "==>" << partons[0]->PDGName() << endl;
} else {
partons[0]->colourNeighbour(partons[1]);
partons[0]->antiColourNeighbour(partons[1]);
// cout << "Colour connecting : "<< partons[0]->PDGName() << "<==>"
// << partons[1]->PDGName() << endl;
}
} else {
// 2 gluon or q-qbar decay
double Theta, Phi;
Kinematics::generateAngles(Theta, Phi);
Energy p1, p2;
p1 = partons[0]->mass();
p2 = partons[1]->mass();
if(p1 == 0.0) p1 = gluMass;
if(p2 == 0.0) p2 = gluMass;
Kinematics::twoBodyDecay(p.momentum(), p1, p2, Theta, Phi,
products[0], products[1]);
for(unsigned int i = 0; i<partons.size(); i++) {
partons[i]->set5Momentum(products[i]);
//cout << *partons[i] << endl;
//cout << products[i] << endl;
}
int first, second;
if(partons[0]->id() > 0) { first = 0; second = 1; }
else { first = 1; second = 0; }
partons[first]->antiColourNeighbour(partons[second]);
if(abs(partons[first]->id()) == ParticleID::g)
partons[first]->colourNeighbour(partons[second]);
//cout << "Colour connecting : "<< partons[0]->PDGName() << "<-->"
//<< partons[1]->PDGName() << endl;
}
if( HERWIG_DEBUG_LEVEL >= HwDebug::full) {
generator()->log() << "QuarkoniumDecayer::Decaying " << p.PDGName()
<< " via " << dm.tag() << "...\n";
}
if( HERWIG_DEBUG_LEVEL >= HwDebug::full) {
generator()->log() << "QuarkoniumDecayer::Decaying " << "...Done\n";
}
//cout << "done decaying\n";
return partons;
}
void QuarkoniumDecayer::persistentOutput(PersistentOStream &os) const {
os << MECode << global;
}
void QuarkoniumDecayer::persistentInput(PersistentIStream &is, int i) {
is >> MECode >> global;
}

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